Drying kiln



J. 1.. BACHRICH Sept. 22 1964 DRYING KILN 4 Sheets-Sheet 1 Filed March6, 1961.

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DRYING KILN Filed March- 6, 1961 I i v I 4 Sheets-Sheet 3 INVA'NTOR(IA/(O 8 L. BAG/ RICH Sept. 22, 1.964

J. L. BACHRICH DRYING KILN 4 Sheets-Sheet 4 Filed March 6; 1961 nwewrokJAKOB 1.. BACHRKH United States Patent Canada Filed Mar. 6, 1961, Ser.No. 93,795 3 Claims. '(Cl. 34191) This invention relates to kilns fordrying lumber and other hygroscopic materials.

This kiln is designed particularly for drying lumber, but it may be usedfor drying any materials that may be stacked and through which air maybe circulated, such as peat moss. The material may be stacked on itself,or it may be stacked in trays or other supporting means. For the sake ofconvenience, the invention will be described in connection with dryinglumber.

Lumber is dried in kilns in order to make it available to the market ina shorter time than it would be if it were allowed to dry naturally.However, with the drying kilns of the prior art, it has not beenpossible to dry the lumber reasonably evenly throughout the kiln. Inorder to be economically possible, the kilns have to be large enough tohold a considerable quantity of lumber in stacked form. The lumber isstacked in layers with spaces therebetween in order to permit heated airto move therethrough. The problem has been that the heated air alwaystends to take the easiest and shortest route through the stacks so thatsome portions of them are dried faster and to a greater degree thanother portions thereof.

One of the main objects of the present invention is the provision of adry kiln with air circulating means therein which will dry the lumberevenly throughout the stack. This is accomplished by providing a kilnconsisting of a drying chamber including drying sections extending sideby side longitudinally thereof and open to each other. Circulating meansis provided at each drying section and arranged to move air transverselyof its section in a direction opposite to that of the circulating meansof the other section. The kiln also includes baffle means for directingair from both circulating means vertically along sides of stacks intheir respective drying sections, and additional baflie means fordirecting air from the opposite vertical sides of the stacks back to thecirculating means. Each of said circulating means is positioned tocirculate air past the bafiie means and through the stack in its dryingsection and back to said circulating means. The air moving verticallybetween the stacks acts as a curtain between the drying sections. ingthe direction of flow of the air from the circulating means so as tobalance the heating effect through the stack in a transverse direction.This arrangement ensures an even distribution of the air circulatingthrough the stacks and, therefore, results in even drying of the lumberor other material.

The circulating system of this kiln makes it possible to attain furtheradvantages. It makes it possible in eifect to divide the drying chamberof the kiln longitudinally into a plurality of drying area. Each areahas its own circulating system, heating means and controls so thatstacks of lumber of different types or diiferent moisture conditions maybe simultaneously dried and each brought to a desired moisture state.

A drying kiln according to the present invention may have means forheating the circulating air either within the drying chamber orexternally thereof.

Two examples of the present invention are illustrated in theaccompanying drawings, in which:

FIGURE 1 is a plan view of a preferred form of drying kiln,

Means is provided for reversice FIGURE 2 is a vertical cross sectiontaken on the line 2-2 of FIGURE 1,

FIGURE 3 is a longitudinal vertical section taken on the line 33 ofFIGURE 2,

FIGURE 4 is a vertical cross section similar to FIG- URE 2 through analternative form of drying kiln, and

FIGURE 5 is an isometric view of the drying air system for the kiln ofFIGURE 4, part of said kiln also being shown.

Referring to FIGURES 1 to 3, 10 is a drying kiln particularly for dryingstacks of lumber. The kiln may be only one stack long, but it ispreferable to make it long enough to accommodate several stacks placedend to end. Kiln 10 includes a base 12, side Walls 13 and 14 and a roof15. The kiln constitutes a drying chamber 18 which includes dryingsections 20 and 22 extending side by side longitudinally of the chamberand opening to each other at 23, said opening 23 extendinglongitudinally and centrally of the drying chamber. Drying section 20 isadapted to receive one or more stacks of lumber 26, while section 22 isadapted to receive one or more stacks of lumber 28. These are standardlumber stacks in which the lumber is piled with transverse spacers sothat air may circulate therethrough. The stacks may be moved into andout of drying sections 21 and 22, the standard meth 0d of doing thisbeing illustrated in the drawings. A plurality of dollies 32 supporteach stack 26 and ride on rails 33 extending into and, usually, throughsection 20. Similarly, each stack 28 is carried by a plurality ofdollies 36 riding on rails 37 extending through section 22. Kiln 10includes end walls 40 and 41 having doors 42 and 43 therein. Thisarrangement makes it possible to extend rails 33 and 37 right throughthe drying sections and out of both ends of the kiln. However, it isobvious that one end of the kiln may be completely closed, in whichcase, the rails would extend out of the opposite end thereof.

By referring to FIGURE 2, it Will be seen that stacks 26 and 28 arespaced respectively from side walls 13 and 14 to form therebetween outerpassages 46 and 47. The opposite sides of the stacks are spaced fromeach other to form a common central vertical passage 49.

A cover 52 extends longitudinally of drying section 20 just above thelevel of the top of stack 26, said cover having flanges 53 and 54depending therefrom along its longitudinal edges. Similarly, anothercover 58 extends longitudinally of section 22 above the stack level andhas side flanges 59 and 60 depending therefrom. Cover 52 defines thebottom of a circulating chamber 63 above the stack area 64 beneath saidcover. Cover 58 also forms a circulating chamber 67 above stack area 68in drying section 22. A bafiie 71 extends downwardly from roof 15 midwaybetween side Walls 13 and 14 of chamber 18 and projects downwardly alittle into central passage 49, terminating near the level of the topsof stacks 26 and 28. Baffle 71 also forms a divider between circulatingchambers 63 and 67.

Circulatin chamber 63 communicates at one end with outer passage 46 andat its opposite end with central passage 49. Suitable circulating meansis mounted in chamber 63, and in this example, the circulating meanscomprises one or more fans 75 located substantially midway between Wall13 and bafiie 71. It is preferable to provide a bulkhead 76 extendingthe length of the kiln above cover 52 and dividing chamber 63 into twoparts. This bulkhead has an opening 77 for each fan 75 and in which saidfan is located, see FIGURES l and 2. The number of fans depends upon thelength of the drying kiln, and there usually are a plurality of thesefans spaced from each other in a longitudinal direction relative to thekiln, see FIGURE 1. The fan 75 is preferably of the type havingreversible and variable pitch blades. As this type of fan and itscontrols are well-known, it does not need detailed description herein.When fan 75 is in operation, it draws air from outer passage 46 anddirects it into central passage 49, or it draws air from said centralpassage and directs it into said outer passage.

Circulating chamber 67 is provided with circulating means in the form ofone or more fans 78, there being one of these fans for every fan 75, andthey are of the same type as the latter. Fans 78 are located in openings79 in a bulkhead 80 extending longitudinally of the kiln above cover 53and dividing chamber 67 into two parts. The blades of fan 78 are alwaysset to oppose the blades of fan 75 or, in other words, these fans arealways blowing in directions opposite to each other, and their controlsare synchronized so that when the direction of one fan is changed, thatof the other is also changed.

Fans 75 and 78 may be mounted and driven in any desired manner. Each mayhave its own motor, but is preferable to mount each pair of fans 75 and78 on a common shaft 80 which extends transversely of drying chamber 18and through circulating chambers 63 and 67 and is carried by suitablebearings 81. One end of each shaft 80 projects outwardly through wall 13and has a pulley 32 on said outer end which is connected by a belt 83 toa double pulley 84 mounted on the drive shaft of a suitable source ofpower, such as an electric motor 85 mounted on the top of kiln 111. Byhaving a double pulley 8 motor 85 may be used to drive two shafts 80 inthe kiln. As there are usually many of these shafts in a kiln, severalmotors 85 are required.

Fan 75 moves air longitudinally through circulating chamber 63, thedirection of movement depending upon the setting of the fan blades. Itis desirable constantly to add fresh air to and to remove some stale airfrom the stream of air circulated by the fan. For this purpose, pipes91) and 91 extend through the kiln roof 15 above and on opposite sidesof fan 75 to provide air passages through said roof. Pipe 91 preferablyhas an opening 94 at its lower end facing the fan, while pipe 91 has anopening 95 at its lower end also facing the fan. Control dampers 98 and99 are located in pipes "Ni and 91 respectively, and these are operatedin any desired manner, and they are preferably interconnected so thatthey open and close together. For this purpose, linkage 11111 isprovided for controlling both of these dampers, said linkage in thisexample being operated by a suitable source of power, such as apneumatic motor 1131. The air travelling through circulating chamber 63is heated in any convenient manner, such as by means of groups 1115 and1% of steam coils located in the chamber above passages 46 and 19. Thesesteam pipes are connected to a suitable source of supply, not shown. Itis desirable at times to inject moisture into the circulating air, suchas at the beginning of a drying cycle, and for this purpose, a spraypipe 16% is provided in the circulating stream of air, and in thisexample, pipe 108 is located at the end of chamber 63 above outerpassage 46.

The air travelling through circulating chamber 67 is conditioned in thesame manner as that travelling through chamber 63. Pipes 112 and 113extend through roof 15 on opposite sides of fan 78 and have dampers 116and 117 therein controlled by linkage 118 operated by a pneumatic motor121). Steam coils 125 and 126 are located in chamber e7 above passages49 and 47, and a spray pipe 128 is provided in said chamber above outerpassage 47.

The condition of the air circulated by fans 75 and 78 may be regulatedmanually or automatically by controlling the temperature thereof bymeans of the steam coils in the circulating chambers, but addingmoisture to the air by means of the spray pipes, and/ or controlling theamount of air entering and leaving the circulating chambers through thepipes in the kiln roof at the two fans. As the actual means of effectingthese controls through wet and dry bulbs in the drying chambers is doneaccording to standard practice, this does not need description herein.

However, the actual apparatus for regulating the condition of thecirculating air is such that kiln 10 may be divided lengthwise into aplurality of drying areas and the condition of the circulating air maybe controlled in each area in accordance with the necessities for thelumber in that area. For example, the illustrated kiln 10 is dividedlongitudinally into two drying areas 132 and 133. Each of these areasincludes a pair of drying sections 20 and 22 located side by side, and apair of circulating chambers 63 and 67. Each of the areas 132 and 133also includes a plurality of fans and 78; steam pipes 105, 106, and12.6; spray pipes ms and 128; and vent pipes 90, 91, 112 and 113. Withthis arrangement, the condition of the air circulating in drying area132 may be different from that circulating in drying area 133.

The general operation of drying kiln 10 is quite simple. Fans 75 and 78are operated to circulate air through drying sections 20 and 22 in whichthey are located. These fans move the air in opposite directions, thatis, they either move the air in their respective circulating chambers towards each other or away from each other. In FIGURE 2, arrows 136 and137 indicate that the fans are blowing the air towards each other. Thisair is deflected downwardly by baffle 71 vertically through centralpassage 49 between stacks 26 and 28. The air passes through the stacksand up outer passages 46 and 47 and back to the fans. This circulatedair travels through the heating coils during its course from the fansand back thereto. With this set-up, the fans create a high pressure areain passage 49, and low pressure areas in outer passages 46 and 47, andthis causes the air to travel transversely through the lumber stacks.After the fans have operated in this direction for a predeterminedperiod, they are reversed so that they direct the air away from eachother, as indicated by arrows 138 and 139 in FIGURE 2. This air strikesside walls 13 and 14 of the kiln which act as baffles and direct itdownwardly into passages 46 and 47. After travelling through the lumberstacks, the air travels upwardly in central passage 49 back to the fans.This change of the direction of flow of the air eliminates thepossibility of the stacks drying more on one side thereof than on theother side.

Regardless of which way the fans are moving the air, the combined streamof air moving vertically through passage 49 in either an upward ordownward direction forms a curtain between drying sections 20 and 21and, therefore, the stacks in said sections. When this central curtainof air is moving upwardly, baffie 71 divides it between the circulatingchambers 63 and 67.

FIGURES 4 and 5 illustrate an alternative form of drying kiln 10a whichfunctions in the same manner as kiln 111, the only difference being inthe apparatus for conditioning the air circulated by the fans throughthe lumber stacks in the drying sections. Vents 90, 91, 112 and 113;coils 105, 1116, 125 and 126; and baflle 71 have been omitted from kiln16a. The apparatus for controlling the condition of the circulating airmay be designed for a kiln having only one drying section, but theillustrated apparatus is for two drying areas 132a and 133a. As theapparatus for these sections is identical, one only will now bedescribed, namely, apparatus for drying area 132a.

FIGURE 5 more or less diagrammatically illustrates the apparatus forthis purpose.

The air to be circulated in the drying kiln is heated in a suitableheating device, such as a furnace or heat exchanger 150. Heated air isdrawn from the furnace through a duct 152 in any desired manner, such asby a blower 153 driven by a suitable source of power, not shown, and isdirected through another duct 156 that extends inwardly beneath kiln 10aand communicates at its inner end with a longitudinal duct or plenumchamber 157 extending along the kiln beneath central passage 49a. Aplurality of pipes 160 extend upwardly from duct 157 through passages49a, there usually being two of these pipes for each pair of fans 75aand 78a. Each pipe 160 has branch pipes 162 and 163 extending laterallyfrom its upper end in opposite directions to circulating chambers 63aand 67a, said branch pipes terminating respectively adjacent fans 75a.and 78a. It is preferable to provide the outer ends of pipes 162 and 163with T-sections 166 and 167 which extend substantially parallel to thevertical planes of their respective fans.

In place of baffle 71 of kiln 1t}, kiln 1111a has a central bathe 171)depending from root a of the kiln between chambers 63a and 67a. Thisbaffle is formed at its upper end with a hollow section or duct 171which extends longitudinally of the kiln. This duct is formed by walls173 and 174 that diverge from bafiie 170 upwardly to roof 15a. Duct 171is actually V-shaped in cross section, see FIGURE 5, and opens throughthe kiln roof. This duct communicates with another duct or plenumchamber 177 which extends longitudinally of the kiln and communicateswith the intake of furnace 158 through a duct 179. Duct walls 173 and174 are formed with holes 181 and 182 throughout the length thereofwhich bring ducts 171 and 177 into communication respectively withcirculating chambers 63a and 67a. Suitable control means is provided inthis duct system for venting some or all of the wet air therein toatmosphere outside the kiln and this is preferably in the form of adamper 186 located in duct 187 extending from duct 179 to heat exchanger158 and positioned to control an opening 188 in said duct 187, saiddamper being manually or automatically controlled in any convenientmanner. Damper 186 may be swung from one position closing opening 188downwardly to an inclined position completely closing duct 187, saiddamper when open directing some or all of the air moving along duct 187out of the system through opening 188.

As stated above, drying kiln 10a functions in the same manner as kiln10. The air circulated by fans 75a and 78a travels through the stacks indrying sections a and 22a. The difference between the two kilns is thatin kiln 10a, the air for the circulating system is heated outside thekiln by furnace 150, and fresh air is supplied to the drying sectionsthrough ducts 152, 156 and 157; central pipes 160, branch pipes 162 and163; and T-sections 166 and 167. This air is discharged into thecirculating chambers 63a and 670: adjacent fans 75a: and 78a. Some ofthe circulating air passes through openings 181 and 182 into duct 171 atthe upper part of baflie 170, and this air travels along ducts 177, 179and 187 back to furnace 150. If desired, some of this air may bedirected out of the system through duct opening 188, while new air maybe added to the system near the furnace in any convenient manner, suchas through a controlled opening 189 in duct 187. The temperature of theair being supplied to the drying kiln is controlled through the furnaceor heat exchange unit. If it is desired to increase the humidity of theair being circulated through the drying sections of the kiln, moisturemay be added to said air by means of spray pipes 108a and 128a incirculating chambers 63a and 670.

What I claim as my invention is:

1. In a dry kiln for lumber and the like stacked for circulation of airtherethrough, an elongated drying chamber having a base, side walls,roof and end Walls, said chamber including first and second elongateddrying sections extending side by side longitudinally thereof and opento each other, each of said first and second drying sections beingadapted to receive at least one lumber stack supported by the basethereof and spaced from a side wall of the chamber, a circulating fan atthe top of each drying section arranged to blow air transversely of itssection, the fan at the top of the first drying section being adapted toblow air in a direction opposite to that of the fan of the secondsection, a central hollow baffie of substantially V-shape cross sectionextending the length of the drying chambers and extending downwardlyfrom the chamber roof between the fans and terminating near the toplevel of the lumber stacks, said central bailie having holes in the Vthereof facing generally towards the fans, outlet bafie meanscommunicating with said central duct and extending to a hot air heatingdevice, inlet duct means extending from the heating device to andthroughout the length of the drying sections, circulating means in thebaffle means adapted to move air from the outlet duct means through theheating device and through the inlet duct means, a plurality of inletpipes extending from said inlet duct means upwardly between the dryingsections throughout the length of the latter, branch pipes extendinglaterally from an upper end of each inlet pipe in opposite directionsand terminating near the fans to supply hot air from the heating deviceto said fans, said fans being positioned selectively to circulate airdrawn from between the stacks towards the chamber side walls that act asbattles to direct said air downwardly or to circulate air drawn frombetween the stacks and the chamber side walls towards the central bafliewhich is positioned to direct said air downwardly in two streams side byside between the stacks, in either case the air being circulatedtransversely through the stacks and the air moving between said stacksacting as a curtain between the drying sections, and means for reversingthe direction of flow of the air from the fans, some of said circulatingair from the stacks being drawn into the central duct through the holesthereof by the circulating means in the duct means and into the outletduct means, passing through the heating device and returning through theinlet duct means and the inlet and branch pipes.

2. A drying kiln as claimed in claim 1 including a T- section at the endof each branch pipe near a fan and extending across the path of airmoved by said fan.

3. A drying kiln, and control means in the duct means operable to permitsome air to enter said duct means as claimed in claim 1 includingadjustable control means in the duct means for venting some air fromsaid duct means to atmosphere outside the kiln.

References Cited in the file of this patent UNITED STATES PATENTS1,541,443 Thelen June 9, 1925 1,840,523 Mueller Jan. 12, 1932 2,085,634Cobb June 29, 1937 2,315,285 Dennington Mar. 30, 1943 2,538,888 SmithJan. 23, 1951 FOREIGN PATENTS 9,173 Australia Sept. 13, 1932 66,155Norway Apr. 27,. 1943

1. IN A DRY KILN FOR LUMBER AND THE LIKE STACKED FOR CIRCULATION OF AIRTHERETHROUGH, AN ELONGATED DRYING CHAMBER HAVING A BASE, SIDE WALLS,ROOF AND END WALLS, SAID CHAMBER INCLUDING FIRST AND SECOND ELONGATEDDRYING SECTIONS EXTENDING SIDE BY SIDE LONGITUDINALLY THEREOF AND OPENTO EACH OTHER, EACH OF SAID FIRST AND SECOND DRYING SECTIONS BEINGADAPTED TO RECEIVE AT LEST ONE LUMBER STACK SUPPORTED BY THE BASETHEREOF AND SPACED FROM A SIDE WALL OF THE CHAMBER, A CIRCULATING FAN ATTHE TOP OF EACH DRYING SECTION ARRANGED TO BLOW AIR TRANSVERSELY OF ITSSECTION, THE FAN AT THE TOP OF THE FIRST DRYING SECTION BEING ADAPTED TOBLOW AIR IN A DIRECTION OPPOSITE TO THAT OF THE FAN OF THE SECONDSECTION, A CENTAL HOLLOW BAFFLE OF SUBSTANTIALLY V-SHAPE CROSS SECTIONEXTENDING THE LENGTH OF THE DRYING CHAMBERS AND EXTENDING DOWNWARDLYFROM THE CHAMBER ROOF BETWEEN THE FANS AND TERMINATING NEAR THE TOPLEVEL OF THE LUMBER STACKS, SAID CENTRAL BAFFLE HAVING HOLES IN THE VTHEREOF FACING GENERALLY TOWARDS THE FANS, OUTLET BAFFLE MEANSCOMMUNICATING WITH SAID CENTRAL DUCT AND EXTENDING TO A HOT AIR HEATINGDEVICE, INLET DUCT MEANS EXTENDING FROM THE HEATING DEVICE TO ANDTHROUGHOUT THE LENGTH OF THE DRYING SECTIONS, CIRCULATING MEANS IN THEBAFFLE MEANS ADAPTED TO MOVE AIR FROM THE OUTLET DUCT MEANS THROUGH THEHEATING DEVICE AND THROUGH THE INLET DUCT MEANS, A PLURALITY OF INLETPIPES EXTENDING FOM SAID INLET DUCT MEANS UPWARDLY BETWEEN THE DRYINGSECTIONS THROUGHOUT THE LENGTH OF THE LATTER, BRANCH PIPES EXTENDINGLATERALLY FROM AN UPPER END OF EACH INLET PIPE IN OPPOSITE DIRECTIONSAND TERMINATING NEAR THE FANS TO SUPPLY